Abstract

We present a laboratory experiment in a large directional wave basin to discuss the instability of a plane wave to oblique side band perturbations in finite water depth. Experimental observations, with the support of numerical simulations, confirm that a carrier wave becomes modulationally unstable even for relative water depths k0h < 1.36 (with k the wavenumber of the plane wave and h the water depth), when it is perturbed by appropriate oblique disturbances. Results corroborate that the underlying mechanism is still a plausible explanation for the generation of rogue waves in finite water depth.

This work has been supported by the European Community's Sixth Framework Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB IV within the Transnational Access Activities, Contract No. 022441. F.W.O. Project G.0333.09 and E.U. Project EXTREME SEAS (Contract No. SCP8-GA-2009-234175) are also acknowledged. L.F. and J.M. acknowledge the Hercules Foundation and the Flemish Government department EWI for providing access to the Flemish Supercomputer Center. L.C. acknowledges the support of the MyWave EU funded FP7-SPACE-2011-1/CP-FP Project.

23.S. Haver and J. Andersen, “Freak waves: Rare realizations of a typical population or typical realizations of a rare population?” in Proceedings of the 10th International Offshore and Polar Engineering (ISOPE) Conference, Seattle, USA, May 2000.

Abstract

We present a laboratory experiment in a large directional wave basin to discuss the instability of a plane wave to oblique side band perturbations in finite water depth. Experimental observations, with the support of numerical simulations, confirm that a carrier wave becomes modulationally unstable even for relative water depths k0h < 1.36 (with k the wavenumber of the plane wave and h the water depth), when it is perturbed by appropriate oblique disturbances. Results corroborate that the underlying mechanism is still a plausible explanation for the generation of rogue waves in finite water depth.

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Experimental evidence of the modulation of a plane wave to oblique perturbations and generation of rogue waves in finite water depth